Imaging sensors used in digital imaging devices such as digital cameras rely on the storage of charge to represent the amount of light that has struck a particular sensor element. Under normal operation, an image exposure begins when the shutter is opened and the imaging sensor is electronically reset, and the exposure ends when the shutter closes. Since the shutter is a mechanical device, the exposure time is primarily determined by the accuracy of the shutter closing time.
Unfortunately, the actual shutter closing time is usually a function of several uncontrolled variables such as temperature, mechanical wear, camera orientation, and other factors. These factors vary in a non-linear manner with environment and over the life of the camera. Therefore, even calibration at the factory cannot fully compensate for this problem. These difficulties become especially apparent for very short exposure times (e.g., 1/2000 of a second and shorter).
It is thus apparent that there is a need in the art for an improved digital imaging device shutter calibration method and apparatus.